Maybe they shouldn't have splitted the game in chapters tbh,put all the missions in the same bag and present the game as whole..it could've lessen the impact and/or make the huge nosedive in quality less noticeable.
Add a hard,extreme,etc mode for every mission(like in GZ) instead of using old missions with a new difficulty and pretend they're new ones.
Maybe it was not that easy to notice during your first play because you're not paying too much attention,miss details etc but the story structure and pacing from ch1 is very well done,you follow these little clues that each mission provides as if you were a detective so you can narrow the search a little bit more:
You find kaz -> He sents you to kill this commander-> Then you find some info about a cargo that may be linked to cypher etc etc -> you finally find Skullface's HQ.
After the fight with ST-84 i was like "damn this game is fucking awesome and this is just the first chapter.." but then CH2 begins and the story structure and pacing starts to fall apart,you wonder why do you need to play old missions to get a new one and forget the motives of why are doing stuff;all of the sudden you're looking for film canisters,codetalker's old research which leads to nothing but to increase your collection of tapes.
Mission 46 coming out of nowhere was the big "what the fuck" moment in this game,what triggered this event? how come all of the sudden Venom remembers what happened? The ending itself is satisfactory but the way it was presented may be the reason for the divisive reception.
It took me a few months to digest it but i kinda appreciate the vagueness of certain aspects of the story because it allows the player to complete the missing link as you see fit,do you wanna believe that this is all VR? or that the medic does not exists and it's just big boss suffering schizophrenia? it's all possible in the end.
If certain inconsistencies,details are there on purpose to feed your imagination and invest time in your own fan theory about what could've happened then kudos to Kojima,as a Dark Souls fan i really appreciate it; But it's still possible that everything was rushed and he couldn't double-check every single detail..or maybe he is just a hack lol.
Well,this is my current position about mgsv and it may change in the future because i still don't know what to make of this game tbh.
Sorry for the big wall of text.